Machine cables are typically used to provide an electrical connection for mobile electrical machines. For example, in the mining or petroleum industry often large electrical machinery is used and each machine cable may have to provide power in the order of a few hundred kilowatts. Typically such power is delivered with a voltage of one or more kilovolts. The cables usually comprise a plurality of cores and are connected using connectors having sockets and pins.
FIG. 1 shows a cross-sectional representation of an electrical connector for connecting a socket with a core of such a machine cable. The Figure shows the socket 10 arranged to receive a pin (not shown). The Figure also shows a thimble 12 which has an open end-portion 13 arranged to receive the core of the machine cable. Fingers of the socket 10 are biased by spring 15 so that an electrical connection with the pin may be achieved. However, the biasing force of the spring 15 may decay over time and it may be necessary to replace the spring 15 and/or the socket 10 from time to time. For this purpose the socket is realisable connected to the thimble 12. The thimble 12 has a threaded portion 14 and the socket 10 has a bore 16. The threaded portion 14 and the bore 16 are arranged to receive stainless steel screw 18 which engages socket 10 and thimble 12 via intermediate part 11. To reduce the likelihood that the stainless steel screw 18 may loosen over time, the stainless steel screw 18 is inserted with a spring washer 19. Socket 10 and thimble 12 have matching conical contact surfaces that match those of intermediate part 11.
FIG. 2 shows a variation of the connector shown in FIG. 1. In this case contact surfaces of socket 20 and thimble 22 do not match when the device is dissembled. However, when the stainless screw 18 is inserted into the bore 24 of the socket 20 and received by the threaded portion 26 of the thimble 22, the contact surface of the socket 20 bents the contact surface of the thimble 22 outwards.
Both prior art devices have the disadvantage that the screw has to be relatively small as the screw head is positioned within the socket. However, the relatively small screw often does not provide sufficient strength for the connection of the socket with the thimble. Further, the contact surfaces are relatively small and the additional pathway that is provided for the current through the screw itself is often not satisfactory. The current has to pass through up to three interfaces (between socket, intermediate part and thimble or, alternatively, between socket and spring washer, between spring washer and screw head and between the thread of the screw and the thread of the bore) and contact potentials, corrosion and contamination may result in contact resistivity at every interface. Further, the screw and the spring washer themselves may not have satisfying electrical properties.